Crystal contact device



E. G. JAMES ET AL CRYSTAL CONTACT DEVICE Filed Jan. 27, 1950 K W/WQ Dec. 15, 1953 In assembling the device the crystal element 3 and the metallic member i are each secured to the studs 9 on the appropriate discs 2, and each disc is then placed over one end of the collar 5 and secured to the collar by a suitable synthetic resin plastic. The interior of the collar in which the crystal element and the metallic member are now situated is arranged to be hermetically sealed by the plastic by which the discs are secured to the collar. The length of the collar 5 is chosen so that with the crystal element 9 and the metallic member l cooperating therewith of predetermined dimensions and fixed in a predetermined position relative to their supporting discs 2, bringing the two discs into contact with opposite ends of the collar is just suflicient to bring the contact point of the metallic member 4 into contact with the surface of the crystal element 3 at a suitable contact pressure, the metallic member having sufficient resilience to take up manufacturing tolerances in the various dimensions concerned. The outer surface of the collar is next tinned with solder, and the assembly of the collar and disc is inserted into the cylinder until it is in a central position along the length of the cylinder. This may conveniently be arranged by placing the cylinder in an upright position on a flat surface, inserting an annular ring in the cylinder, which annular ring will come to rest on the flat surface, and inserting the assembly into the cylinder until it comes to rest on the annular ring. By making the annular ring of the correct length, the assembly is easily positioned in a predetermined position. The cylinder is then heated sufficiently to melt the solder on the collar, so that on cooling the collar is secured in the required position. The reason for making the discs of slightly smaller diameter than the collar is to ensure that the discs do not bind on the side of the cylinder when inserting the assembly in the cylinder.

It will be understood that in the absence of the collar, due to the fact that the metallic member cooperating with the crystal element is normally of small diameter wire, the characteristic impedance of the portion of the device between the two discs would be undesirably high and would be a substantial mismatch with the adjoining portions. It will be appreciated therefore that the collar serves the dual function of maintaining the discs at a predetermined distance apart and of reducing to a more desirable value the characteristic impedance of that portion of the device bounded by the collar, that is the portion between the two discs.

Figure 2 illustrates a slightly modified arrangement of the device which without departing from the scope of the present invention presents an alternative method of obtaining a good point contact between the crystal element and the co-opcrating metal member. In this case the metallic stud 6 associated with the metallic member 4 is concentrically bored throughout its length, the bore 9 being tinned and of a diameter sufficient to accommodate a metal rod in upon which the co-operating metal member is mounted to be passed therethrough and which after adjustment is secured in position by heating the device suificiently to allow the tinning to melt; any excessive projection of the metal rod 19 being severed after soldering.

Although the invention has been described with reference to a double-ended form of crystal contact device, it is to be understood that it is equally applicable to a single-ended crystal contact dedisc no longer being necessary in this case as the coaxial line is connected only to the other end of the cylinder. Moreover, although the collar has been described as a separate member from the cylinder, the collar may in fact be provided integral with the cylinder by forming the cylinder with an intermediate portion of reduced internal diameter. The separate collar is preferred as the integral collar is more difficult to produce to the required degree of accuracy. Moreover, the collar may be of insulating material, provided that the inner surface at least is provided with a metallic coating which is efiectively electrically connected to the cylinder, at any rate at the radio frequencies concerned, so that the collar can still serve to reduce to a more desirable value the characteristic impedance of that portion of the device bounded by the collar.

W e claim:

1. A crystal contact device for use at a radio frequency, said device comprising a hollow metal cylinder, a collar whose inner surface is metallic, said collar being disposed wholly within the metal cylinder, the outer surface of said collar being in contact with the juxtaposed portion of the inner surface of the cylinder over the entire length of the collar, said inner surface of the collar being effectively electrically connected to the cylinder at said radio frequency, a crystalline element and associated supporting member, and a cooperating metal member and associated supporting member, said supporting members being of disc form and situated one against each end of the collar, said crystalline element, said cooperating metal member and said associated supporting members being disposed wholly within the metal cylinder, and said crystalline element and said cooperating metal member being disposed wholly within the collar.

2. A crystal contact device in accordance with claim 1 wherein the collar is metallic.

3. A crystal contact device in accordance with claim 1 wherein the collar is metallic and formed integrally with the hollow metal cylinder.

4. A crystal contact device in accordance with claim 3 wherein the supporting members are of insulating material.

5. A crystal contact device in accordance with claim 4 wherein the crystalline element and the cooperating metal member are coaxially situated within the hollow metal cylinder.

6. A crystal contact device in accordance with claim 1 wherein the collar is metallic and the supporting members are of insulating material.

EMRYS GWYNNE JAMES. AUBREY OSCAR, EDGAR LINDELL.

I References Cited in the file of this patent UNITED STATES PATENTS Number Name Date D. 156,501 Gates Dec. 20, 1949 2,406,405 Salisbury Aug. 27, 1946 2,415,841 Ohl Feb. 18, 1947 2,429,823 Kinman Oct 28, 1947 2,438,110 Brattain Mar. 23, 1948 2,469,569 Ohl May 10, 1949 2,560,579 Kock July 17, 1951 2,560,606 Shive July 17,1951 

